1. Field of the Invention
The present invention relates to a tire condition monitor device mounted on a tire wheel of a vehicle such as automobiles and provided with a circuit board for detecting a pneumatic pressure in a tire and a method of manufacturing the tire condition monitor device.
2. Description of the Related Art
Conventional tire condition monitor devices of the above-described type comprises a circuit board on which a pressure sensor is mounted, and a casing accommodating the circuit board. For example, JP-A-2005-119370 discloses one of such conventional tire condition monitor devices. As in general electric appliances, a coating process is applied to the circuit board and the casing is then filled with silicon resin for improvement of gas barrier properties (or gas permeability) and moisture-proof properties, whereby the circuit board is protected. For example, JP-A-S62-61392 discloses such circuit board.
However, the tire condition monitor devices are used under the specific environment of being subject to a high-pressure gas containing corrosion components (sulfur constituent, for example) in a tire. Thus, further improvements in the gas barrier and moisture-proof properties have been required of the tire condition monitor devices.